Study On The Influence Of Deep Foudation Excavation On The Adjacent Existing Subway Tunnel

The emergence of the subway has effectively solved the problem of urban traffic congestion.However,the increasing tension of the urban above-ground space has caused the above-ground and underground structures of construction projects to develop more and more in the direction of "high and deep",which will inevitably have an impact on the surrounding buildings and the environment,especially such as subway tunnels,which are very sensitive for deformation.Sufficient attention should be paid to the structures.Taking a deep foundation pit project adjacent to Metro Line2 in Zhengzhou City as the background,the influence of deep foundation pit construction in Zhengzhou silt soil layer on the deformation of adjacent existing subway interval tunnels is studied.This paper analyzes the influence of various factors in the foundation pit engineering on the displacement of the tunnel structure and the unloading of foundation pit excavation on the surrounding soil,supporting structure,etc.Through statistical engineering case monitoring data,theoretical analysis,numerical simulation,and field measurement.The influence mechanism of the adjacent tunnels,a three-dimensional finite element numerical model was established in accordance with the engineering design drawings and construction plan to verify the feasibility of the existing plan,and the accuracy of the numerical calculation results was verified through the comparative analysis of the on-site monitoring data and the numerical calculation results.The main research contents and conclusions are as follows:(1)According to the basic situation of the foundation pit,the safety level of the foundation pit was determined;according to the existing relevant standards and specifications,the relevant deformation control standards of this project were determined.(2)Based on the analysis of actual foundation pit engineering monitoring data of 20 adjacent subway tunnels,numerical analysis method was used to study the relative position relationship of foundation pit tunnels,space-time effect,underground water,supporting structure selection and other factors.The law of deformation of adjacent subway tunnels under excavation was summarized.(3)For this kind of foundation pit project adjacent to the subway tunnel,the deformation mechanism analysis of the soil,supporting structure,and tunnel displacement caused by unloading of foundation pit excavation was carried out.(4)A three-dimensional finite element model was established based on a deep foundation pit project of a nearby subway tunnel,and the feasibility of the construction plan was verified through numerical calculation results,and the law of soil,double-row piles,and subway tunnel displacement caused by the excavation of the foundation pit was analyzed.(5)The displacement value and change trend of the field monitoring and numerical simulation results were basically the same,which verified the accuracy of the numerical model and also proved the feasibility of the construction plan of this project.